Process for the production of alkali-earth metal permanganates



Patented July 13, 1925.

GFFEQEU' RGBERT E. WILSQN, LEON RV. PAESQNS, AND STJFXHLEY L.CBLISI-IQLM, OF CAMBRIDGE, MASSACHUSETTS, ASSIGITORS TO THE SECRETARY OF'WAR THE UNTTED STATES OF AMERICA, TRUSTEE.

PROCESS FOR THE PRODUCTION OF 'ALKALLEARTH METAL PERMANGANATES.

No Drawing. Original application filed September 27, 1918, Serial No.255,975.

tion filed. July 17, 1922.

(GRANTED UNDER THE ACT OF The invention described herein may be used bythe Government, or any of its oilirers or employes in prosecution ofWork for the Government, or by any other person in the United States,Without payment of any royalty thereon.

This application. is a division cl our copending application, Serial No.250,975, filed leptemher 27, 1918, which has matured into Patent No.l,el53,562 or May 1, 1923.

The present invention relates to the production of alkali earth metalpermanganates and especially the permanganates of calcium and magnesiumas these have been found to b. very etiicient oxidizing agents forcertain purposes, more elicient even than the permanganates of thealkali metals. This superiority is shown in the so-called British sodalime granules.

lilore specifically, the object of the invention is the development ofta commercial process of producing the alkali earth metal permanganates,since so far as We are aware, their manufacture in quantity has neverbeen attempted on a large scale or even on a small scale, except inGermany, Where they have been produced by a rather expensiveelectrolytic process starting with potassium permanganate (KMnOQ.

We have discovered that calcium or magnesium permanganate cannot beprepared directly by ordinary methods but that indirect methods must beused, e. g. by first r'orming a manganate, oxidizing this, and

neutralizing the permanganic acid so formed with barium, calcium ormagnesium hydroxide.

ll e have investigated very thoroughly the possible methods of makingcalcium permanganate and believe that only "four of them are at allworkable. These are:

(1) Preparation of silver permanganate by crystallization from slowlycooled solutions of silver nitrate and potassium or sodium permanganate.Calcium permanganate is then formed metathetically by treatment withcalcium chloride.

(2) Selective transference and oxidation electrolysis of sodium or ;potassium.- manga:

Divided and this applica Serial No. 575,761.

MARCH 3, 1883; 22 STAT. L, 625.)

nate or permanganate and milk of lime or a calcium salt.

(3) Electrolysis of ferromanganese anode into solution of a calciumsalt.

Preparation of barium manganatc by fusion or wet methods, conversion topermanganate by oxidation or acidification, metatheses into calciumpermanganate by treatment with calcium sulphate or milk of lime.

Oi these tour possible methods: (1) is not a possible large scale methodon account of its use of silver; (2) and are electrolytic methodsWithout a great deal of prominc, and are to be considered elsewhere; (4)is the principal subject of this application.

Three distinct methods for preparing barium (or strontium) manganatehave been here investigated. The first of these methods involves heatingtogether barium peroxide, hydroxide, or a salt, such as the nitrate orchlorate, With an oxide of manganese, as manganese dioxide in thepresence of air or oxygen. Considerable Work has been done upon fusionsof this type, and beautiful green products were obtained, but the mostfavorable results obtained gave products containing only 810% BaMDO, therest of the product consisting of residual M110 B210 and the BaMnO, fromthe thermal decomposition of the manganese. The thorough mixing of suchdry sinterings is rather diliicult, but quite necessary; indeed even thefusions should be stirred to giye the bestresults.

The second and more preferable of these methods involves the reaction ofsimilar mixtures in a low melting fused medium, such as fused sodiumhydroxide, or sodium nitrate at temperatures well below a red heat. hecooled fused mass is extracted with Water, the filtrate containingchiefly NaOH or Nal 'O being evaporated to dr ness, and the fusionmedium being returned to the process. The insoluble residue consists ofa basic barium mangani-manganate containing 32% BaMnO together withexcess M110 etc. This represents a decided gain over the first, or dryfusions.

slight solubility in water, giving an acid solution of exceedingly lowhydrogen ion concentration, and in consequence drives the reaction tocompletion,'m:ainly by removing insoluble equilibrium products.

This reaction is complete and irreversible on account of theinsolubility of the products formed, but, as might be expected from theslight solubility of both the reacting substances, carbon dioxide andbarium manganate, the solubility of the latter being comparable tobarium sulphate, the rate of reaction is practically negligible atordinary temperatures and very slow even at the boiling temperature. Thegreat advantage of carbonation for converting barium manganate lies inthe very pure product to be obtained by this method.

By using sulphuric acid in place of carbon dioxide, a soluble reactingsubstance is sub stituted for a very slightly soluble one and thus therate of reaction is greatly increased at the corresponding temperatures.Two of the reaction products are as before insoluble. The use of thisacid, however, produces such a high hydrogen ion concentration that itis no longer possible to work above ordinary or room temperatures onaccount of the spontaneous decomposition of permanganic acid.

This decomposition is appreciable even at low temperatures,

This reaction is apparently also retarded by the insoluble productbarium sulphate which seems to have a mechanical retarding elfect uponthe yet undissolved manganate, apparently by the formation of aninsoluble coating upon the particles. This increases the amount ofdecomposition by increasing the length of treatment required for complete conversion and requires the use of excess H SO In the CO processthe reaction can be stopped when Ba-(MnQQ is ol tained according to theequation:

Theoretically, it would appear that the same result would follow byusing H SO ac cording to the equation and actually this must be passedthrough as an inte'mediate stage, but in order to obtain completeconversion of the manganate, enough acid must be added to carry thereaction still further to the following stage BSMIIQOQ H2SO4 B31SO42HM1104. By adding Ca (OH) 2 to this reaction mixture, calciumpermanganate is obtained. This is essentially the equivalent of addingCaSO, in the alternative method, except that the process is carried outin two stages, i. e., first the steps of precipitating the B11804 by theH SQ, and then the neutralization out the i-lMnO, by means of Ca(OH.) Itmilk of lime is employed for the neutralization the resulting filteredsolution of calcium permanganate is of course contaminated with calciumsulphate.

In the case of nitric acid there is again one soluble reactingsubstance, in this resembling the action of sulphuric acid, but. with anadditional soluble product, this lat-- ter involving an impurity in thefinal product obtained. Upon the other hand the reaction proceeds sorapidly in the cold that decomposition is reduced to a minimum. As withsulphuric acid, however, at least some excess of nitric acid is requiredin oroer to work with the requisite rapidity due in this case to thefact that the reaction products are not as insoluble as before, andthere is apparently a measurable equilibrium set up before the reactionis complete.

The nitric acid has absolutely no direct oxidizing action in thisprocess, its action is solely that of an acid.

it barium hydroxide is used to neutralize the permanganic acid and anyexcess nitric acid, the resulting solution contains barium nitrate andpermanganate. By evaporation it is possible to concentrate therelatively more stable barium perinan anate and separate the lesssoluble bari n. nitrate ll calcium hydroxide is used tor thisneutralization and the clear filtrate concentrated by evaporation, theleast soluble salt barium nitrate first tends to separate out, followedby calcium nitrate until. when concentrated to about a 20% Ca(Mn O,).only about 5% CMNOQ remains in solution and a much smaller proportion otBa(NO-,)

As an example o't our process the following experiment was carried out.liters Oil green liquor made by leaching the mass from an ordinaryNaOlrll-lilnO fusion containing of sodium manganate and 24.3% of causticalkali, part or which was in the Form of carbonate, was boiled for 5hours with l kilograms of hydrated lime to remove the carbonate. Thesludge was removed by decantation and filtration and 12 liters of thefiltrate containing 3.4%- of sodium inauganate as boiled with 1 kilogram of hydrated barium hydroxide for one hour. The solution graduallybecame purplish but the green color of manganate still persisted andsuccessive treatments with two portions of grams each of bariumhydroxide for on hour each followed. The

C ll solution was cooled and filtered. The dried precipitate was apurplish blue color and contained about 1 kilogram oi 7l% bariummanganate.

ims of the 7.4% barium manganate was suspended in one half liter ofwater and was treated with successive portions of diluted nitr-icacid (1to 10 each portion being htly in excess of that theoretically requiredto. produce complete conversion, The reacting mass was kept cool at alltimes. The final residue was entirely converted Without requiring theboiling with sodium carbonate which it was necessary to employ tocomplete the con version when carbonic or sulphuric acids were used. Themass was filtered and Washed and the filtrate neutralized and C-Oll.cent-rated to barium permanganate, the crystals of nitrate being removedafter cooling. Calcium sulphate was addedto precipitatebarium sulphate.The yield of cal: oium.permangan ate Was 91.8 92 of the theoretical. Thetotal time oft treatment was tour hours It is to be understood that bythe teru i alkali earth, we include calcium, barium, strontium andmagnesium.

This invention is not limited to the specific details set forth in theforegoing examples which should be construed as illustrative and not byWay of limitation, and in iew of the numerous modifications which may beeffected therein without departing from the, spirit and scope of thisinvention, it is desired that onlv such limitations be imposed as areindicated in the appended claims.

lVe claim as ourinvention:

1. In a process of making alkali earth metal permanganates, thesubprocess of producing barium manganate which comprises fusing ahydroxide of an alkali metal and adding to the fused mass bariumperoxide and an oxide ot mange ese in an oxidizi lg atmosphere.

In; a process or" making alkali earth metal permanganates, thesubprocess ot' produeingbarium manganate which comprises fusing a hydrXide'of an alkali metal and adding to the fused mass barium peroxide andmanganese dioxide.

3. In a process oi-maliing alkali earth metal permanganates, thesubprocess of producing barium manganate which comprises fusing sodiumhydroxide and adding to the fused mass barium peroxide and manganesedioxide.

l. In a process oi making alkali earth metal perma 'iganates thesubprocess of producing barium manganate which comprises fusing bariumperoxide, an oxide of manganese and ,1 hydroxide of an alkali metal inan oxidizing atmosphere 5. In a process of making alkali earth metalpcrmanganates, the subproeess of producing barium nianganate whichcomprises fusing barium perozgide and manganese dioxide with a hydroxideof an alkali metal.

R BER E- ILS I LEON VJ. PARSONS. STANLEY L. CHISHOLM.

